The present invention relates to a barrel shifter circuit and, more particulaly, to a barrel shifter circuit having a rotation function designed in an integrated circuit device (IC).
A previously known barrel shifter circuit having a rotating function has the arrangement as shown in FIG. 1. In FIG. 1, a data bus 101 is connected with a unidirectional n-bit barrel shifter 102 the output from which is sent to the data bus 101 through a data latch output buffer circuit 103. An n-bit shift control signal group 104 is also inputted to the above n-bit barrel shifter 102. A data latch control signal 105 and an output control signal 106 are supplied to the data latch control circuit 103.
Now, referring to FIG. 2, an explanation will be given of the operation of the above conventional barrel shifter circuit having a rotating function. Now, it is assumed that rotation of 5 (five) bits is intended. First, the data on the n-bit data bus 101 are inputted to the unidirectional barrel shifter 102. If a 5-bit shifting signal is selected in the n-bit shift control signal group 104, leftward rotation of 5 bits will be carried out, and the output lines corresponding to the respective rotated bits will be connected with the data latch output buffer circuit 103. The respective bits thus rotated will be sent out to the data bus 101 under the control of the output control signal 106.
The above conventional barrel shifter circuit having a rotating function has the following defects. Since it uses a unidirectional n-bit barrel shifter 102, it requires the number n.times.n of transfer gates (marked with .largecircle. in FIG. 2) corresponding to n bits.times.n bits, and so requires a relatively large area. Also, each of the output lines corresponding to the respective bits, which is connected through the n number of the transfer gates corresponding to the n bits, provides a relatively large load capacitance. This means that the above conventional barrel shifter circuit is unsuited to a high speed operation.